One of the objectives of a computer graphics display system user is to have the ability to draw polygons, or groups of polygons, made up of a number of potentially overlapping contours. These contours may be self intersecting and lacking any information regarding their state. There are two major methods of filling a polygon, the winding rule and the odd-even fill rule, the latter being implemented by the present invention. The majority of graphics adapters currently being used are capable of filling simple, convex polygons, but are not able to fill multiple contour, possibly self-intersecting, free space polygons, except on a scan line basis which is an extremely inefficient method of resolving these complex polygons and requires careful consideration of special cases to avoid incorrect rendering of these polygons. It should be noted that hardware solutions to this problem are presently known, but are not able to provide the level of compatibility and efficiency, achieved by the present invention.
It would be very desirable to be able to resolve these complex polygons into a group of simple, convex polygons which can then be filled by a conventional graphics adapter.